JPS609872B2 - Corrosion prevention treatment method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a novel anticorrosion treatment method.

One method of transporting fluids such as oil and gas is to construct pipelines using steel pipes.

One problem with such methods is that the steel pipes corrode.

Various methods have been explored to prevent corrosion of steel pipes. One method is to protect the surface of the steel pipe with noise materials.

However, this method has a problem in that the phosphorescent material layer is easily damaged by external impact. In recent years, methods of coating the steel pipe surface with plastics such as polyethylene and polyvinyl chloride have been explored as a method to solve the problems of such methods.

The following three methods are generally known for coating the surface of steel pipes with plastics. 1. A method of heating a steel pipe, applying an undercoat composition to the surface, coating the surface with molten plastic, and cooling.

2. A method of processing plastics into a cylindrical heat-shrinkable pipe in advance, attaching this to a steel pipe whose surface has been coated with an undercoat composition, and heating the pipe to shrink and cover it.

3. Plastics are formed into a tape shape in advance, and an adhesive layer is formed on one surface of the tape, and this is wrapped in a spiral shape overlapping parts of the steel pipe surface, which has been coated with an undercoat composition. How to cover.

In this way, coated steel pipes protected by plastics are
Compared to coated steel pipes protected with the above-mentioned bonito greens, it has remarkable effects in terms of corrosion prevention effect and service life, but
Coated steel pipes protected by plastics are exposed to harsh conditions, which can cause damage to the coating.

In addition, due to the demand for more reliable corrosion protection, cathodic protection methods are now being used in combination. The cathodic protection method is a method of preventing corrosion of steel pipes by applying a voltage of around 2V to coated steel pipes.

However, even in this method, electrolysis occurs due to the electric current applied for cathodic protection at the damaged part of the plastic, which causes peeling between the undercoat composition layer and the steel pipe surface (generally called cathodic peeling). When water enters the peeled portion, the peeling further expands.

For this reason, it has been found that there is a drawback that current leaks from this peeled part, voltage decreases, the cathodic protection effect disappears, and corrosion progresses. The present inventors believed that if this problem of cathode peeling could be solved, the cathodic protection method would be extremely useful as a corrosion protection method for coated steel pipes, and as a result of various studies on methods to solve cathode peeling - mixtures made of specific materials. It was discovered that the problem could be solved by treating the surface of the steel pipe using a method, and this result led to the present invention. That is, the present invention is characterized in that when forming a protective layer on the surface of a metal article such as a T-steel pipe, the surface of the article is treated with a mixture containing a malleable elastic material and a phenolic resin as essential components. The present invention provides an anticorrosion treatment method that prevents the protective layer from peeling off from the surface of the article through cathodic protection.

The reason why the anticorrosion treatment method of the present invention has cathodic peeling resistance is not clear, but according to the findings obtained from the results of repeated experiments conducted by the present inventors, ``the malleable elastic material and the phenolic resin are not necessarily resistant to cathodic peeling. It is thought that the phase separation effect due to insufficient phase lag characteristics is also due to the adhesive effect due to the hydrogen bonding force generated between the hydroxyl group in the phenolic resin and the metal oxide present on the surface of the metal article. Ru.

The malleable elastic material used in the present invention is capable of maintaining the thickness for a predetermined period of time when a mixture is formed into a uniform thickness by coating on the surface of a metal article, and imparting a predetermined elasticity to the mixture layer. For example, rubbers, ethylene copolymers, etc. are used. According to our experiments, natural rubber, polyisoprene rubber, non-polar rubbers such as butyl rubber, styrene-butadiene rubber to ethylene-propylene rubber, ethylene-propylene-gene terpolymer rubber, and/or modified products thereof. It has been found to be favorable.

Furthermore, the phenolic resin used in carrying out the present invention includes not only novolac type, resol type, and terbene-modified type resins, but also other types of resins modified with alkylphenols and the like.

As is generally known, when a phenolic resin is represented by a general formula, it has an alkyl group, and the smaller the number of carbon atoms in this alkyl group, the better the cathodic peeling resistance.

The preferable number of C is 8 or less. Regarding resol type phenolic resins, those with a low degree of methylolization are preferable because the resin will not gel even if the mixture is exposed to high temperatures after use.

Commercially available products of the phenolic resin used in the present invention include Tonovolak type, manufactured by Arakawa Forestry Chemical Industry Co., Ltd. under the trade name Yumanor 10, 510, 530, and Sumitomo Chemical Co., Ltd. under the trade names PR-317, 50775, and Kuni. There are products such as RP-600 manufactured by Sakae Kagaku Kogyo Co., Ltd. and RP-11078 and PR-50232 manufactured by Sumitomo Durez Co., Ltd. as resol types.
"Manufactured by Arakawa Forestry Chemical Industry Co., Ltd. Product name: Tamanol 52 Melon L Do 5
21, 520 Gunei Chemical Industry Co., Ltd. Product name: AP-107D
-Tackirol 201 manufactured by Sumitomo Chemical Co., Ltd. Terbene-modified types include SP Misaki 553 and SP 560 manufactured by Schenectady Co., Ltd., Sumilite Resin PR-12603 manufactured by Sumitomo Durez Co., Ltd. LTP and Yasuhara manufactured by Hercules Co., Ltd. Product name: YS Polyster # manufactured by Yushisha Co., Ltd.
1150 etc.

The blending ratio of the malleable elastic material and the phenolic resin is ~former:latter=10.2-6, practically 130.4
~5 (all weight ratios), and if the resin content is less than this, the cathode peeling resistance is insufficient, and if it is more than this, the elasticity of the mixture layer will be lost and it will be easily damaged by external impact, so it is preferable. It's something that doesn't exist.

A suitable amount of compounding agents such as a colorant, a filler, a softener, an adhesion-imparting resin, and an anti-aging agent can be added to the mixture containing the above-mentioned substance and a resin as essential components, if necessary.

The mixture is generally used dissolved in one or more solvents such as toluene, xylene, hexane, hebutane, industrial gasoline, ethyl acetate, methyl ethyl ketone, methyl alcohol, and ethyl alcohol.

The solids content in the mixture solution is preferably about 10-4% by weight. The mixture solution is applied to the surface of metal articles such as steel pipes with a brush, spray, or other appropriate coating device to a solid content of 0.005 to 0.05.
It is applied to a thickness of 0.3, preferably 0.02 to 0.1, and the surface of the metal article is treated. The treated surface is then coated with plastics such as polyethylene, polyvinyl chloride, or other protective materials.

The coating method is not particularly limited. When coating plastics, an undercoat composition can also be applied to the treated surface to improve the adhesion effect with the protective coating. The coated metal products* treated with the anticorrosion treatment method of the present invention are characterized in that they do not cause cathode peeling even when energized for cathodic protection, and can provide sufficient anticorrosion effects over a long period of time. has. Examples of the present invention will be shown below.

Example 1 100 g of natural rubber was dissolved in 500 g of toluene, 70 g of each of the phenolic resins shown in Table 1 was added thereto, and 30 g of terbene resin, 30 g of calcium carbonate, and 2 g of carbon black were added. to obtain a mixture solution.

Table 1 shows the test results of Example 1, and the peeling length in the table shows the result of a cathode peeling test conducted according to ASTM G-8 (the same applies hereinafter).

Table 1 Example 2 Butyl rubber was dissolved in hebutane, and terbene-modified (binene-modified) resin (trade name YS) was added per 10 parts by weight of butyl rubber.
Polyster #1150) was added as shown in Table 2.
(unit weight part) to obtain a mixture solution with a solid content of 25% by weight.

Table 2 Example 3 100 parts of grafted rubber obtained by grafting 5 parts by weight of methacrylic acid ester to 10 parts by weight of natural rubber was dissolved in 300 parts of a mixed solvent of toluene:methyl ethyl ketone = 7:3, and a novolac type phenol resin was dissolved in this. (trade name Tackirol 101) 100 ml and rosin ester resin 40 ml were added to obtain a mixture solution.

The peeled diameter length of this mixture was 5 legs.

Comparative Example Instead of the phenolic resin of Example 1, various resins shown in Table 3 are added to obtain a mixture solution.

Table 3 As is clear from the above examples, according to the anticorrosion treatment method of the present invention, the fact that the cathode peeling characteristics are extremely good is remarkable.

Claims (1)

[Claims] 1. When forming a protective layer on the surface of a metal article such as a steel pipe, the surface of the article is treated with a mixture containing a malleable elastic material and a phenolic resin as essential components. An anticorrosion treatment method for preventing peeling of the protective layer from the surface of the article by electrolytic protection. 2. The anticorrosion treatment method according to claim 1, wherein the malleable elastic material is a non-polar rubber. 3. The anticorrosion treatment method according to claim 1, wherein the blending ratio of the malleable elastic material and the phenolic resin is 1:0.2 to 6 (weight ratio).